1. Field of the Invention
The present invention relates to a sheet feeding apparatus incorporated in a cash dispenser, optical reader or similar equipment and, more particularly, to a method and an apparatus for sequentially feeding sheets such as bills, original documents or paper sheets one by one.
2. Description of the Prior Art
A sheet feeding apparatus for the above application usually has a storing section which stores a great number of bills, paper sheets or similar sheets therein, and a stage movable up and down in the storing section, as taught in, for example, Japanese Utility Model Laid-Open Publication No. 68335/1989. When the stage loaded with a stack of sheets is elevated to a predetermined feed position, the apparatus is ready to feed the sheets from the storing section, uppermost one being first. A pair of pick-up rollers are positioned at spaced locations along the length of the stack of sheets and rotated to pay out the uppermost sheet from the feed position. A pair of feed rollers are located in close proximity to the front end of the storing section with respect to the intended direction of sheet feed and in parallel with the pick-up rollers. The sheet paid out by the pick-up rollers is further driven by the feed rollers in the feed direction to a transport path which is contiguous with the storing section. It is a common practice to operatively connect the feed rollers and pick-up rollers by belts and pulleys and drive them by a single motor at the same speed in the feed direction. Such a configuration, however, needs a great number of parts including the belts and pulleys for interconnecting the feed rollers and pick-up rollers and the motor for driving the rollers, increasing the overall size of the apparatus. Moreover, pulleys and belts complicate the structure of the apparatus.
It often occurs that two or more of the sheets stacked on the stage adhere to one another due to static electricity or a similar cause and are fed out together unseparated. To eliminate such an occurrence, a reverse roller is associated with each of the feed rollers in such a manner as to contact the sheet underlying and paid out together with the uppermost sheet. The reverse rollers are rotated in the same direction as the feed rollers, i.e., in a counter-feed direction opposite to the feed direction. As a result, the sheet contacting the reverse rollers is urged backward, i.e., toward the storing section and thereby separated from the overlying or uppermost sheet. The degree of separation of the sheet depends on the gap between the feed rollers and the associated reverse rollers. An adjusting screw is affixed to the shaft of each feed roller in order to adjust the position of the feed roller. Specifically, should the gap between the feed rollers and the reverse rollers be greater than a predetermined one, the reverse rollers would fail to separate the underlying sheet from the overlying sheet and would cause the latter to entrain the former out of the storing section. Conversely, should the gap be smaller than the predetermined one, an excessive pressure applied on the sheets should act to delay the feed of the sheet of interest. Moreover, since one of the feed rollers and one of the reverse rollers are provided in a pair and locate at one of opposite sides of the stage in the left-and-right direction, any difference in gap between the right and left pairs would cause the sheet to skew with respect to the feed direction. The adjusting screws each being associated with respective one of the feed rollers have to be adjusted to eliminate the above occurrences. However, this adjustment is a measure to be taken after an error has occurred in the feed of sheets and, therefore, lacks in immediate adaptability. Feed errors cannot be fully eliminated by the conventional apparatus since the nip of the rollers tends to change due to the friction between the rollers and the friction between the rollers and the sheets. Even an implementation for automatically adjusting the gap between the feed rollers and the reverse rollers would fail to achieve a satisfactory result since the adjustment of the gap is delicate, minute and difficult.
When all the sheets intervening between the pick-up rollers and the stage have been fed out by the pick-up rollers, the pick-up rollers contact and rub against the stage to produce noise. Moreover, both the pick-up rollers and the stage wear in contact with each other, adversely effecting the feed of sheets.